Art of mounting electron discharge devices



ITH

July 194 ART OF MOUNTING ELECTRON DISCHARGE DEVICES Filed Jan. 51. 1941 ttorm WY m Patented July 6, 1943 ART OF MOUNTING ELECTRON DISCHARGE DEVICES Rogers M. Smith, Ashland Terrace, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 31, 1941, Serial No. 376,865

Claims.

This invention relates to the art of mounting electron discharge devices and has special reference to the mounting and shielding of tubes designed for use at high and ultra high frequencies.

One problem encountered in the operating of electron discharge tubes at high and ultra high frequencies is that of maintaining certain of the tube elements, and the leads thereto, at ground potential with respect to the radio frequency employed. In an efiort to solve this problem, it has previously been proposed to incorporate miniature capacitors in the tube socket so that the bypass or ground connections are made as close as possible to the tube elements, whereby feedback between the external and internal circuit elements is minimized. Such mountings, however, are not entirely satisfactory, especially at ultra high frequencies, since the fixed by-pass (shunt) capacitors which are incorporated in the socket have no eifect upon the internal or inter-electrode coupling which obtains by reason of the inherent inductances and other coupling factors of the structure within the envelope of the tube.

Accordingly, the principal object of the present invention is to provide a combined shield and socket incorporating means for obviating the foregoing and other objections to prior art methods of mounting tubes designed to operate at high and ultra high frequencies.

The foregoing and other objects are achieved in accordance with the invention by the provision of a combined shield and socket incorporatingone or more adjustable capacitors capable of series-resonating the inductances of the tube leads so that the ground potential is reflected to the desired points within the tube envelope.

Certain details of construction together with other objects and advantages will be apparent and the invention itself will be best understood by reference to the following specification and to the accompanying drawing, wherein Figure 1 is a vertical section view of a socket and tube assembly embodying the invention,

Figure 2' is a horizontal sectional View taken on the line 2-2 of Fig. 1,

Figure 3 is a bottom plan view of the device of Figs. 1 and 2,

Figure 4 is a vertical sectional View taken on the line 4-4 of Fig, 2 and showing the tuned anode connector,

Figure 5 is a circuit diagram for one of the electrodes 'of the tube and mount shown in Figs. 1 to 4.

In the drawing wherein like reference characters designate the same or corresponding parts in all figures, 2 designates generally a cylindrical metal shell or container comprising a lower or body portion 2a and a removable upper or cover portion 21) which is adapted to be fitted on the body 2a. Snugly seated within the body of the container 2, as on a rim 4, is an insulating cylindrical insert 6 which in turn is shown provided with an inwardly extending rim portion 8' upon which a number (in this case, twelve) of preferably bifurcated spring contacts H] are mounted in a position to receive a similar number of radially extending prongs 12 of an acorn or other type electron discharge tube M. (The tube shown in the drawing is an orbital-beam secondary-emission amplifier," RCA tube type A5588A.) Two of these spring contacts, in this case the one, Illa, which is positioned to receive a prong for the control grid and the one, [02), which is positioned to receive the prong for the anode, are connected, respectively, to oppositely located stiff wire or rod-like members 5 (see Fig. 3) each of which comprises the inner conductor of a resonant concentric line whose outer conductor preferably comprises a pipe [8 which extends into the body of the shell 2 through and in contact with the base thereof. A shorting plug which may comprise insulated inner and outer cores 20 and 22 which are mounted within the pipe I8 for slidable movement on the inner conductor l6, and which is accessible through a longitudinal slot 13a in the pipe, provides a convenient means for variably tuning the anode and grid circuits. But one resonant line is shown in Fig. 4; it will be understood, however, that the control grid and anode connectors may be of duplicate construction, if desired.

The other prong receiving contacts I 0 are connected to short leads 24 which terminate in preferably fiat cylindrical plates 25 which are fitted in recesses provided for the purpose in the outer surface of the insulating support 6, i. e., facing but not touching the inner periphery of the cylindrical casing 2. These plates 26 comprise the fixed armatures of a plurality of adjustable capacitors whose adjustable armatures comprise a similar number of threaded metal plugs 28 which are received in tapped holes in the circumferential wall of the casing, in radial register with the fixed armatures 26. Since the casing 2 is constituted of metal it comprises an efiective "ground for the adjustable armatures 28. Mica or equivalent dielectric inserts 30 may be provided if desired between the opposed faces of the armatures 26 and 28. As shown more clearly in Fig. 1 each of the plug-like armatures 28 may be provided with a kerf 28k on its outer surface for receiving the blade of a screw driver or other adjusting tool, not shown.

The short leads 24 which connect the spring contacts l2 with the fixed armatures 26 also may comprise terminals to which appropriate electrical elements such for example as the miniature resistors 30, choke coils 32, and fixed filter capacitors 34 may be connected. In this case the elements which are designed to carry direct current (e. g. parts 30 and 32) are provided with insulated leads 3B which may be brought out through holes 38 in the base of the casing 2 and connected to terminals 40 at the outside of the casing. As shown more clearly in Fig. 3, the terminals 40 to which the leads 36 are connected may be mounted on insulating terminal boards or strips 42 on the bottom surface of the casing. The fixed capacitors 34, on the other hand, may be ground-connected to the casing as through bent-up lugs 44 on an annulus 46 which is provided for the purpose on the inner bottom surface of the casing. Additional fixed by-pass capacitors 48 may be connected between the terminals 40 and the outer bottom surface of the container wherever necessary or desirable.

It would needlessly complicate the drawing to Show the circuit connections to all of the numerous elements of the now standard ultra-high frequency tube of the drawing; accordingly, referring to Fig. 5, reference will be made to but one typical circuit. In this figure, the screen grid lead lflc of the tube is supplied with a direct current bias through the series connected choke coil 32 and resistor 30. Fixed capacitors 34 and 48 (they are so numbered in Figs. 1 and 3) are provided for filtering out extraneous alternating current components. The variable capacitor, comprising the fixed armature 26 and adjustable armature 28, are connected between the grid I and ground (1. e., the metal casing 2). By adjusting the variable armature 28 (as by means of a screw driver inserted in the kerf 28k of the plug 28, Fig. 1) the circuit comprising the inherent inductance of the electrode H and its terminals, and the capacitance of the condenser 2628 is brought to series resonance at the operating frequency, whereby the inductance (inherent in the electrode and its leads and which otherwise would give rise to undesired internal coupling effects) is tuned out or neutralized.

Various other embodiments of the invention will suggest themselves to those skilled in the art. It is to be understood, therefore, that the foregoing description of a preferred embodiment is to be interpreted as illustrative of the inven tion and not in a limiting sense, except as required by the spirit of the appended claims.

What is claimed is:

1. A mount for an electron discharge tube comprising a metal housing containing a socket having a plurality of contacts mounted to receive the terminals of said tube, a plurality of armature plates individual to said socket contacts mounted in circumferentially spaced relation within said housing and presented in useful capacitive relation to the inner surface of said housing whereby said armatur plates and said housing comprise a plurality of capacitors having a common armature, and means connecting said socket contacts to the capacitor armatures which are individual thereto.

2. The invention as set forth in claim 1 and wherein means are provided on the exterior of said metal housing for varying the capacitance of said capacitors.

3. The invention as set forth in claim 1 and wherein said metal housing is provided with an opening, a terminal board adjacent said opening on an exterior surface of said housing, and a plurality of leads connected to said contacts and extending through said opening to said terminal board.

4. The combination with an electron di charge tube having an envelope provided with a plurality of radially extending terminals, of a socket base for said tube comprising a plurality of contacts mounted in circumferentially spaced array on said base in position to receive said radially extending terminals, and a plurality of variable capacitors mounted on said base in line with said terminals and contacts.

5. A mount for an electron discharge tube comprising a metal housing provided with a tapped hole in a wall thereof, a threaded metal plug adapted to be accommodated in said tapped hole and comprising one armature of a capacitor, a second armature mounted within said housing in capacitive relation with respect to said first mentioned armature, an insulating support within said housing, a contact for a terminal of said tube on said insulating support and an electrical connection between said contact and second men tioned capacitor armature.

ROGERS M. SMITH. 

